include/linux/compiler_attributes.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_COMPILER_ATTRIBUTES_H
   3 #define __LINUX_COMPILER_ATTRIBUTES_H
   4
   5 /*
   6  * The attributes in this file are unconditionally defined and they directly
   7  * map to compiler attribute(s) -- except those that are optional.
   8  *
   9  * Any other "attributes" (i.e. those that depend on a configuration option,
  10  * on a compiler, on an architecture, on plugins, on other attributes...)
  11  * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
  12  *
  13  * This file is meant to be sorted (by actual attribute name,
  14  * not by #define identifier). Use the __attribute__((__name__)) syntax
  15  * (i.e. with underscores) to avoid future collisions with other macros.
  16  * If an attribute is optional, state the reason in the comment.
  17  */
  18
  19 /*
  20  * To check for optional attributes, we use __has_attribute, which is supported
  21  * on gcc >= 5, clang >= 2.9 and icc >= 17. In the meantime, to support
  22  * 4.6 <= gcc < 5, we implement __has_attribute by hand.
  23  *
  24  * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
  25  * depending on the compiler used to build it; however, these attributes have
  26  * no semantic effects for sparse, so it does not matter. Also note that,
  27  * in order to avoid sparse's warnings, even the unsupported ones must be
  28  * defined to 0.
  29  */
  30 #ifndef __has_attribute
  31 # define __has_attribute(x) __GCC4_has_attribute_##x
  32 # define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
  33 # define __GCC4_has_attribute___designated_init__     0
  34 # define __GCC4_has_attribute___externally_visible__  1
  35 # define __GCC4_has_attribute___noclone__             1
  36 # define __GCC4_has_attribute___optimize__            1
  37 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  38 #endif
  39
  40 /*
  41  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  42  */
  43 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
  44
  45 /*
  46  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  47  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  48  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  49  */
  50 #define __aligned(x)                    __attribute__((__aligned__(x)))
  51 #define __aligned_largest               __attribute__((__aligned__))
  52
  53 /*
  54  * Note: users of __always_inline currently do not write "inline" themselves,
  55  * which seems to be required by gcc to apply the attribute according
  56  * to its docs (and also "warning: always_inline function might not be
  57  * inlinable [-Wattributes]" is emitted).
  58  *
  59  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  60  * clang: mentioned
  61  */
  62 #define __always_inline                 inline __attribute__((__always_inline__))
  63
  64 /*
  65  * The second argument is optional (default 0), so we use a variadic macro
  66  * to make the shorthand.
  67  *
  68  * Beware: Do not apply this to functions which may return
  69  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  70  * returning extra information in the low bits (but in that case the
  71  * compiler should see some alignment anyway, when the return value is
  72  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  73  *
  74  * Optional: only supported since gcc >= 4.9
  75  * Optional: not supported by icc
  76  *
  77  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  78  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  79  */
  80 #if __has_attribute(__assume_aligned__)
  81 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  82 #else
  83 # define __assume_aligned(a, ...)
  84 #endif
  85
  86 /*
  87  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  88  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  89  */
  90 #define __cold                          __attribute__((__cold__))
  91
  92 /*
  93  * Note the long name.
  94  *
  95  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  96  */
  97 #define __attribute_const__             __attribute__((__const__))
  98
  99 /*
 100  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 101  * attribute warnings entirely and for good") for more information.
 102  *
 103  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 104  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 105  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 106  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 107  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 108  */
 109 #define __deprecated
 110
 111 /*
 112  * Optional: only supported since gcc >= 5.1
 113  * Optional: not supported by clang
 114  * Optional: not supported by icc
 115  *
 116  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 117  */
 118 #if __has_attribute(__designated_init__)
 119 # define __designated_init              __attribute__((__designated_init__))
 120 #else
 121 # define __designated_init
 122 #endif
 123
 124 /*
 125  * Optional: not supported by clang
 126  *
 127  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 128  */
 129 #if __has_attribute(__externally_visible__)
 130 # define __visible                      __attribute__((__externally_visible__))
 131 #else
 132 # define __visible
 133 #endif
 134
 135 /*
 136  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 137  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 138  */
 139 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 140 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 141
 142 /*
 143  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 144  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 145  */
 146 #define __gnu_inline                    __attribute__((__gnu_inline__))
 147
 148 /*
 149  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 150  */
 151 #define __malloc                        __attribute__((__malloc__))
 152
 153 /*
 154  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 155  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 156  */
 157 #define __mode(x)                       __attribute__((__mode__(x)))
 158
 159 /*
 160  * Optional: not supported by clang
 161  * Note: icc does not recognize gcc's no-tracer
 162  *
 163  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 164  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-optimize-function-attribute
 165  */
 166 #if __has_attribute(__noclone__)
 167 # if __has_attribute(__optimize__)
 168 #  define __noclone                     __attribute__((__noclone__, __optimize__("no-tracer")))
 169 # else
 170 #  define __noclone                     __attribute__((__noclone__))
 171 # endif
 172 #else
 173 # define __noclone
 174 #endif
 175
 176 /*
 177  * Note the missing underscores.
 178  *
 179  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 180  * clang: mentioned
 181  */
 182 #define   noinline                      __attribute__((__noinline__))
 183
 184 /*
 185  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 186  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 187  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 188  */
 189 #define __noreturn                      __attribute__((__noreturn__))
 190
 191 /*
 192  * Optional: only supported since gcc >= 4.8
 193  * Optional: not supported by icc
 194  *
 195  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
 196  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
 197  */
 198 #if __has_attribute(__no_sanitize_address__)
 199 # define __no_sanitize_address          __attribute__((__no_sanitize_address__))
 200 #else
 201 # define __no_sanitize_address
 202 #endif
 203
 204 /*
 205  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 206  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 207  */
 208 #define __packed                        __attribute__((__packed__))
 209
 210 /*
 211  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 212  */
 213 #define __pure                          __attribute__((__pure__))
 214
 215 /*
 216  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 217  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 218  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 219  */
 220 #define __section(S)                    __attribute__((__section__(#S)))
 221
 222 /*
 223  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 224  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 225  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 226  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 227  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 228  */
 229 #define __always_unused                 __attribute__((__unused__))
 230 #define __maybe_unused                  __attribute__((__unused__))
 231
 232 /*
 233  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 234  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 235  */
 236 #define __used                          __attribute__((__used__))
 237
 238 /*
 239  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 240  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 241  */
 242 #define __weak                          __attribute__((__weak__))
 243
 244 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */